Remanufacturing hydraulic pumps

Abstract

A hydraulic pump can be remanufactured to save the investment in its components that are not seriously worn or failed. Some of the worn components, such as the pump barrel and yoke, can be salvaged by replacing or rebuilding the worn features. In particular, a worn internal spline on the pump barrel can be replaced by a spline insert that is threaded to the pump barrel and includes a new internal spline. A worn actuation tab on a yoke for contacting an actuating piston can be replaced by adding a new tab wear button.

1 . A variable displacement hydraulic pump comprising: 
 a barrel which rotates around a rotational axis;    a plurality of cylinders formed in the barrel, each cylinder having a longitudinal axis formed generally parallel to the rotational axis;    a piston positioned inside of each of the plurality of cylinders for movement relative thereto, the pistons moving back and forth in their respective cylinders to pump hydraulic fluid at a first end of each piston;    a yoke, the inclination of the yoke determining the displacement of the pump, a second end of each piston pushing against the yoke when the piston is pumping hydraulic fluid;    a separate wear button attached to the yoke; and    an actuator which pushes against the wear button to adjust the angle of inclination of the yoke.    
   
   
       2 . A variable displacement hydraulic pump according to  claim 1  wherein one of the wear button or the yoke has a projection formed thereon, and the other of the wear button or the yoke has a bore formed therein, and the wear button is attached to the yoke by inserting the projection into the bore in a press fit.  
   
   
       3 . A variable displacement hydraulic pump according to  claim 1  wherein the barrel further comprises: 
 a central opening formed in the barrel generally parallel to the rotational axis;    a separate, annular insert received in the central bore; and    splines formed on an internal surface of the insert adapted for engaging corresponding external splines formed on a drive shaft.    
   
   
       4 . A method of salvaging an axial piston, variable displacement hydraulic pump, the pump comprising a barrel which rotates around a rotational axis, a plurality of cylinders formed in the barrel, each cylinder having a longitudinal axis formed generally parallel to the rotational axis, a piston positioned inside of each of the plurality of cylinders for movement relative thereto, the pistons moving back and forth in their respective cylinders to pump hydraulic fluid at a first end of each piston, a yoke, the inclination of the yoke determining the displacement of the pump, a second end of each piston pushing against the yoke when the piston is pumping hydraulic fluid, an actuator which pushes against a first surface of the yoke to adjust the angle of inclination of the yoke, the method comprising: 
 forming a wear button;    attaching the wear button to the yoke such that the actuator pushes against the wear button to adjust the angle of inclination of the yoke.    
   
   
       5 . A method according to  claim 4  further comprising: 
 providing a projection on one of the wear button or the yoke, providing a bore on the other of the wear button or the yoke; and    wherein attaching the wear button to the yoke further comprises inserting the projection into the bore with a press fit.    
   
   
       6 . A method according to  claim 4  wherein the barrel further comprises a central bore formed therein generally parallel to the rotational axis, and worn splines formed on an internal surface of the central bore adapted for engaging corresponding external splines formed on a drive shaft, the method further comprising: 
 machining a new central bore in the barrel that substantially removes the worn splines;    providing an insert, the insert having a second central bore having internal splines formed on an internal surface of the second central bore, the internal splines adapted for engaging external splines formed on a drive shaft; and    inserting the insert into the new central bore.    
   
   
       7 . A method according to  claim 6  further comprising: 
 forming internal threads on an internal surface of the new central bore;    forming external threads on an external surface of the insert; and    wherein inserting the insert into the new central bore comprises engaging the internal threads on the new central bore with the external threads on the insert.    
   
   
       8 . A method according to  claim 6  further comprising: 
 forming a first shoulder on the barrel;    forming a second shoulder on the insert; and    wherein inserting the insert into the new central bore further comprises engaging the internal and external threads until the first shoulder abuts the second shoulder.    
   
   
       9 . A method of manufacturing and remanufacturing a hydraulic pump comprising: 
 manufacturing a hydraulic pump comprising a barrel which rotates around a rotational axis, a plurality of cylinders formed in the barrel, each cylinder having a longitudinal axis formed generally parallel to the rotational axis, a piston positioned inside of each of the plurality of cylinders for movement relative thereto, the pistons moving back and forth in their respective cylinders to pump hydraulic fluid at a first end of each piston, a yoke, the inclination of the yoke determining the displacement of the pump, a second end of each piston pushing against the yoke when the piston is pumping hydraulic fluid, and an actuator which pushes against a first surface of the yoke to adjust the angle of inclination of the yoke;    placing the hydraulic pump in service with an end user;    receiving the hydraulic pump back from an end user after it has been in service;    remanufacturing the hydraulic pump, the remanufacturing comprising removing the first surface, preparing a wear button, and attaching the wear button to the yoke in place of the first surface such that the actuator pushes against the wear button to adjust the angle of inclination of the yoke.    
   
   
       10 . A method according to  claim 9  wherein remanufacturing the hydraulic pump further comprises: 
 providing a projection on one of the wear button or the yoke, providing a bore on the other of the wear button or the yoke; and    wherein attaching the wear button to the yoke further comprises inserting the projection into the bore with a press fit.